Electrical machines have a stationary element and a movable element. The movable element may be a rotating element or a linearly movable element. The interaction between the stationary element and the movable element is based on the interaction of a magnetic field generated by either the stationary element or the movable element and electric currents in a winding on the movable element or the stationary element, respectively. The interaction is such that the direction of the current, the direction of the magnetic field and the direction of the movement are at substantially right angles to each other, e.g. along an x-direction, a y-direction and a z-direction of a right-angled co-ordinate system.
The winding comprises a plurality of coils wound around teeth of a soft magnetic material normally consisting of steel laminations in order to reduce the eddy currents.
Although the winding can be wound on the stationary element or on the movable element, the following description will be limited to the winding being part of a stator assembly.
Conventionally, the stator assembly of an electrical machine has a stator core formed of a stack of steel laminations. As an alternative to the use of steel laminations, the stator core may be formed from iron powder, as exemplified by U.S. Pat. No. 4,947,065 disclosing a stator moulded in one-piece, and by International Patent Application WO95/12912 disclosing a stator comprising a plurality of separate and substantially identical parts.
By its very nature any compacted, non-sintered material will not be fully dense. This means that soft iron powder currently available will have permeabilities that are lower than the permeabilities obtainable with steel laminations. However, magnetic powder composites could offer advantages such as isotropic magnetic behavior, reduction in iron losses at high frequencies, improved thermal characteristics and flexible design and assembly.